netdev - Re: [PATCH 1/1] eventfd: implementation of EFD

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Message-ID: <5115FC6A.8000603@250bpm.com>
Date:	Sat, 09 Feb 2013 08:36:10 +0100
From:	Martin Sustrik <sustrik@...bpm.com>
To:	Eric Wong <normalperson@...t.net>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Sha Zhengju <handai.szj@...bao.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 1/1] eventfd: implementation of EFD_MASK flag

On 09/02/13 04:54, Eric Wong wrote:

>>> Using one eventfd per userspace socket still seems a bit wasteful.
>>
>> Wasteful in what sense? Occupying a slot in file descriptor table?
>> That's the price for having the socket uniquely identified by the
>> fd.
>
> Yes.  I realize eventfd is small, but I don't think eventfd is needed
> at all, here.  Just one pipe.

Ah. Got you! You mean not to change the kernel, just use pipe for the 
purpose.

However, the convoluted pipe-style design is the problem I am trying to 
solve rather than the solution. It leads to convoluted APIs with 
convoluted semantics as described in the article. I've been using that 
kind of design for past 8 years and every time I have to deal with it I 
swear that one day I will implement a proper in-kernel solution to get 
rid of the hack.

And now I have finally done so.

Martin
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